This invention relates generally to gas appliances and more particularly, to systems and methods for controlling gas flow in gas appliances. Examples of gas appliances include gas-operated cooking appliances, gas-operated baking appliances, gas-operated stoves, gas-operated cookers, gas-operated hobs, and gas-operated ovens. Natural gas, liquid gases and gasified liquids are various types of gases that are used in the gas appliances. Examples of liquid gases include butane and propane and examples of gasified liquids include benzene and spirit. The gases differ in their combustion behavior and their calorific value.
Gas is extracted from a supply device, for example, a gas supply network, a gas cylinder, and a gas tank or reservoir, and fed to a burner of a gas appliance via a gas valve in a gas feed line. An input that changes the position of the valve is effected by a selector operated by a user, for example, by turning an adjustment knob or by selection on a control panel. The selection actuates, for example, opens or closes, the valve located in the gas feed line to set a heat output that is intended by the user. By partial opening or closing of the valve, the gas flow through the gas feed line is changed and thus the heat output that is intended by the user is set. The burner has a burner nozzle, which during operation of the burner constitutes a flow resistance limiting gas flowing from the burner nozzle. The burner nozzle thus determines a maximum gas flow that corresponds to a maximum heat output or heating power of the burner. Types of burners vary with a change in size and shape of the burner nozzle.
Pressure of the gas may vary relative to the atmospheric pressure depending on a gas system used, for example, on the type of the supply device and the type of gas used. Moreover, a valve may exhibit hysteresis in the setting behavior. An example of hysteresis is when the gas flow at the same valve position varies as a function of the length of travel of the valve during the just prior actuation and the direction in which the valve is actuated for setting the intended gas flow.
Because of the gas-pressure fluctuations, and the hysteresis of the valve, the reproducibility and setting accuracy of the gas flow to the valve is inconsistent for any particular setting. No accurately defined heat outputs can be selected by means of the selector. For this reason, the user generally changes the position of the valve until the intended heat output is reached, in the course of which the user is in essence guided by flame size, cooking behavior, or baking behavior of the food.